In communication systems comprising an information transmission link between an information source and an information sink, transmitting and receiving devices are used for information processing and transmission, in which devices
1) the information processing and information transmission can take place in a preferred direction of transmission (simplex mode) or in both directions of transmission (duplex mode), PA0 2) the information processing is analog or digital, PA0 3) the information transmission over the long-distance transmission link is wire-connected or takes place wirelessly on the basis of various FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and/or CDMA (Code Division Multiple Access) information transmission methods--e.g. according to radio standards such as DECT, GSM, WACS or PACS, IS-54, PHS, PDC etc. [Compare IEEE Communications Magazine, January 1995, pages 50 to 57; D. D. Falconer et al.: "Time Division Multiple Access Methods for Wireless Personal Communications"]. PA0 (1) in the form of an image, PA0 (2) as a spoken word, PA0 (3) as a written word, PA0 (4) as a coded word or image. PA0 a) Simulation of the ISDN channel structure (D channel and 2 B-channels), especially of the D channel in the text which follows, PA0 b) good economy of bandwidths; particularly significant for ISDN since some services already need two. DECT channels for the B-channel data rate of 64 kb/s, PA0 c) minimum technical complexity. PA0 Common signalling channel on the C plane for all terminal endpoints TE connected to the ISDN line. PA0 The TE-specific signalling channels to the network are separated there by TE-individual addresses TEI (Terminal Endpoint Identifiers). PA0 Throughput: 16 kb/s PA0 Usage: depends on many criteria, as a rule lower than maximum capacity; congestion situations are possible but can be rapidly cleared because of the high capacity. PA0 Use of TDMA time slots. PA0 In principle, one C.sub.s channel (s=slow) is used per time slot for signalling [C plane in the DECT standard] and an associated channel is used for the user information [U plane in the DECT standard] (32 kb/s throughput). PA0 Throughput of the C.sub.s channel: 2 kb/s. PA0 The C.sub.f channel occupies one time slot. PA0 Throughput of the C.sub.f channel: 25.6 kb/B.
"Information" is a generic term which stands both for the intelligence (information) and for the physical representation (signal). Even if an information contains the same intelligence--i.e. has the same information content--different signal forms can occur. Thus, for example, an information relating to an object, can be transmitted
In this connection, the type of transmission according to (1) . . . (3) is normally characterized by continuous (analog) signals whilst discontinuous signals (e.g. pulses, digital signals) are usually produced in the case of the type of transmission according to (4).
Based on this general definition of a communication system, the invention relates to methods for allocating telecommunication channels of different channel capacity in a hybrid telecommunication system, particularly an "ISDN {character pullout} DECT-specific RLL (Radio Local Loop)/WLL (Wireless Local Loop)" system according to the precharacterizing clause of claim 1.
Hybrid telecommunication systems are, for example, communication systems containing different--wireless and/or wire-connected--telecommunication subsystems.
FIG. 1 shows--representative for the multiplicity of hybrid telecommunication systems--on the basis of the printed documents "Nachrichtentechnik Elektronik, Berlin 45 (1995) Vol. 1, pages 21 to 23 and Vol. 3 pages 29 and 30" and IEE Colloquium 1993, 173; (1993), pages 29/1-29/7; W. Hing, F. Halsall: "Cordless access to the ISDN basic rate service" on the basis of a DECT/ISDN Intermediate System DIIS according to ETSI Publication prETS 300xxx, Version 1.10, September 1996, an "ISDN {character pullout} DECT-specific RLL/WLL" telecommunication system IDRW-TS (Integrated Services Digital Network {character pullout} Radio in the Local Loop/Wireless in the Local Loop) with an ISDN telecommunication subsystem I-TTS [compare printed document "Nachrichtentechnik Elektronik, Berlin 41-43, Part: 1 to 10, P1: (1991) Vol. 3, pages 99 to 102; P2: (1991) Vol. 4, pages 138 to 143; P3: (1991) Vol. 5, pages 179 to 182 and Vol. 6, pages 219 to 220; P4: (1991) Vol. 6, pages 220 to 222 and (1992) Vol. 1, pages 19 to 20; P5: (1992) Vol. 2, pages 59 to 62 and (1992) Vol. 3, pages 99 to 102; P6: (1992) Vol. 4, pages 150 to 153; P7: (1992) Vol. 6, pages 238 to 241; P8: (1993) Vol. 1, pages 29 to 33; P9: (1993) Vol. 2, pages 95 to 97 and (1993) Vol. 3, pages 129 to 135; P10: (1993) Vol. 4, pages 187 to 190"] and a DECT-specific RLL/WLL telecommunication subsystem RW-TTS.
In this arrangement, the DECT/ISDN intermediate system DIIS and, respectively, the RLL/WLL telecommunication subsystem RW-TTS are preferably based on a DECT (Digital Enhanced (previously European) cordless telecommunication)/GAP system DGS; compare (1): Nachrichtentechnik Elektronik 42 (1992) January/February No. 1, Berlin, DE; U. Pilger "Struktur des DECT-Standards" (Structure of the DECT standard), pages 23 to 29 in conjunction with ETSI Publication ETS 300175-1 . . . 9, October 1992; (2): Telcom Report 16 (1993), No. 1, J. H. Koch: "Digitaler Komfort fur schnurlose Telekommunikation {character pullout} DECT-Standard eroffnet neue Nutzungsgebiete" (Digital comfort for cordless telecommunication{character pullout}DECT standard opens up new fields of application), pages 26 and 27; (3): tec 2/93--The technical magazine by Ascom "Wege zur universellen mobilen Telekommunikation" (Approaches to universal mobile telecommunication), pages 35 to 42; (4): Philips Telecommunication Review Vol. 49, No. 3, September 1991, R. J. Mulder: "DECT, a universal cordless access system"; (5): WO 93/21719 (FIGS. 1 to 3 and associated description)]. The GAP (Generic Access Profile) standard is a subset of the DECT standard which has the task of ensuring the interoperability of the DECT air interface for telephone applications (compare ETSI Publication-prETS 300444, April 1995).
As an alternative, the DECT/ISDN intermediate system DIIS and, respectively the RLL/WLL telecommunication subsystem RW-TTS, can also be based on a GSM system (Groupe Speciale Mobile or Global System for Mobile Communication; compare Informatik Spektrum 14 (1991) June, No. 3, Berlin, DE; A. Mann: "Der GSM-Standard--Grundlage fur digitale europaische Mobilfunknetze" (The GSM standard--basis for digital European mobile radio networks), pages 137 to 152). In the context of a hybrid telecommunication system it is also possible, instead, for the ISDN telecommunication subsystem I-TTS to be constructed as a GSM system.
In addition, further possibilities to be considered for implementing the DECT/ISDN intermediate system DIIS and, respectively, the RLL/WLL telecommunication subsystem RW-TTS or the ISDN telecommunication subsystem I-TTS are the systems mentioned initially, and future systems which are based on the known multiple-access methods FDMA, TDMA, CDMA (Frequency Division Multiple Access, Time Division Multiple Access, Code Division Multiple Access) and hybrid multiple-access methods formed from these.
The use of radio channels (e.g. DECT channels) in traditional line-connected telecommunication systems such as the ISDN is gaining increasing significance, particularly against the background of future alternative network operators without their own complete wire-line network.
Thus, it is intended to provide the ISDN subscriber with ISDN services at standard ISDN interfaces by means of the wireless RLL/WLL (Radio in the Local Loop/Wireless in the Local Loop) line interfacing technique, e.g. including the DECT system DS, for example in the RLL/WLL telecommunication subsystem RW-TTS (compare FIG. 1).
In the "ISDN {character pullout} DECT-specific RLL/WLL" telecommunication system IDRW-TS according to FIG. 1, a telecommunication subscriber (user) TCU (Telecommunication User) with his terminal equipment TE (also Terminal Endpoint) is tied in, e.g. via a standardized S interface (S-BUS), the preferably DECT-specific DECT/ISDN intermediate system DIIS (first telecommunication subsystem) contained in the RLL/WLL telecommunication subsystem RW-TTS and constructed as local information transmission loop, a further standardized S interface (S-BUS), a network termination NT and a standardized U interface of the ISDN telecommunication subsystem I-TTS (second telecommunication subsystem) into the ISDN world and all the services available therein.
The first telecommunication subsystem DIIS essentially consists of two telecommunication interfaces, a first telecommunication interface DIFS (DECT Intermediate Fixed System) and a second telecommunication interface DIPS (DECT Intermediate Portable System) which are connected to one another wirelessly, e.g. via a DECT air interface. Because of the quasi-stationary first telecommunication interface DIFS, the first telecommunication subsystem DIIS forms the local information transmission loop defined above in this connection. The first telecommunication interface DIFS contains a radio fixed part RFP, an interworking unit IWUI and an interface circuit INC1 to the S interface. The second telecommunication interface DIPS contains a radio portable part RPP and an interworking unit IWU2 and-an interface circuit INC2 to the S interface. In this arrangement, the radio fixed part RFP and the radio portable part RPP form the known DECTIGAP system DGS.
For a DECT-specific RLL system as bearer for all ISDN services, if possible, in the subscriber loop, the following general problems are given:
Simulation of the D channel
Properties of the D channel:
The order of information items is ensured TE-individually by the access mechanism to -the. D channel.
DECT channels:
FIG. 2 shows the TDMA structure of the DECT/GAP system TKS in accordance with the printed document "Nachrichtentechnik Elektronik 42 (1992) January/February, No. 1, Berlin, DE; U. Pilger: "Struktur des DECT-Standards" (Structure of the DECT standard), pages 23 to 29 in conjunction with ETS 300 175-1 . . . 9, October 1992". With respect to the multiple-access methods, the DECT/GAP system is a hybrid system in which radio messages can be sent on ten frequencies in the frequency band between 1.88 and 1.90 GHz according to the FDMA principle within a predetermined time sequence according to the TDMA principle according to FIG. 2 from the base station RFP to the mobile part RPP and from the mobile part RPP to the base station RFP (duplex mode). The time sequence is determined by a multi-timeframe MZR which occurs every 160 ms and which has 16 timeframes ZR having in each case a duration of 10 ms. Within this timeframe ZR, information relating to a C, M, N, P, Q channel defined in the DECT standard is transmitted separately from the base station RFP and the mobile part RPP. If information for several of these channels is transmitted within one timeframe ZR, the transmission takes place in accordance with a list of priorities, where M&gt;C&gt;N and P&gt;N. Each of the 16 timeframes ZR of the multi-timeframe MZR is, in turn, subdivided into 24 time slots ZS having in each case a duration of 417 .mu.s, out of which 12 time slots ZS (time slots 0 . . . 11) are intended for the "base station RFP.fwdarw.mobile part RPP" direction of transmission and a further 12 time slots ZS (time slots 12 . . . 23) are intended for the "mobile part RPP.fwdarw.base station RFP" direction of transmission. In each of these time slots ZS, information items having a bit length of 480 bits are transmitted in accordance with the DECT standard. Of these 480 bits, 32 bits are transmitted as synchronization information in a SYNC field and 388 bits are transmitted as user information in a D field. The remaining 60 bits are transmitted as additional information in a Z field and as guard information in a "guard time" field. The 388 bits of the D field, transmitted as user information, are, in turn, subdivided into a 64-bit-long A field, a 320-bit-long B field and a 4-bit-long "X-CRC" word. The 64-bit-long A field is composed of a header with a length of 8 bits, a data record with data for the C, Q, M, N, P channels with a length of 40 bits and an "A-CRC" word with a length of 16 bits.
Properties:
The DECT standard also offers other channel structures, e.g. a C.sub.f channel (f=fast).
Based on the OSI/ISO reference model [compare (1): Unterrichtsblatter (Training sheets) Deutsche Telecom Vol. 48, 2/1995, pages 102 to 111; (2): ETSI Publication ETS 300175- 1 . . . 9, October 1992; (3): ETSI Publication ETS 300102, February 1992; (4): ETSI Publication ETS 300125, September 1991; (5): ETSI Publication ETS 300012, April 1992], FIG. 3 shows a model of the C plane of the "ISDN {character pullout} DECT-specific RLL/WLL" telecommunication system IDRW-TS according to FIG. 1.
Based on the OSI/ISO reference model [compare (1): Unterrichtsblatter (Training sheets) Deutsche Telecom Vol. 48, 2/1995, pages 102 to 111; (2): ETSI Publication ETS 300175-1 . . . 9, October 1992; (3): ETSI Publication ETS 300102, February 1992; (4): ETSI Publication ETS 300125, September 1991; (5): ETSI Publication ETS 300012, April 199], FIG. 4 shows a model of the U plane for voice data transmission of the "ISDN {character pullout} DECT-specific RLL/WLL" telecommunication system IDRW-TS according to FIG. 1.
Economy of bandwidths
The C.sub.s channel structure offers optimum economy of bandwidths for a standard voice connection since, according to FIG. 5, on the basis of FIGS. 3 and 4 and taking into consideration the ETSI Publications (ETS 300175-1, 10/1992, Section 7; ETS 300175-3, October 1992, Section 4.1; ETS 300175-4, October 1992, Section 4), only one transmission path (bearer)--e.g. MBC with the LCNy, LCN1 according to FIG. 5--or, respectively, one connection or one time slot is needed.
According to FIG. 5, on the basis of FIGS. 3 and 4 and taking into consideration the ETSI Publications (ETS 300175-1, October 1992, Section 7; ETS 300175-3, 10/1992, Section 4.1; ETS 300175-4, October 1992, Section 4), the use of the C.sub.f channel leads to less economy of bandwidths since the U plane itself-needs a further transmission path (bearer) or, respectively, a further connection or a further time slot; i.e. two bearers--e.g. MBC with the LCN2, LCNZ and MBC with the LCNy, LCN1 according to FIG. 5--or, respectively, two connections or two time slots are needed for a simple voice connection.
Moreover, three bearers--e.g. MBC with the LCNx, LCN0, MBC with the LCNy, LCN1 and MBC with the LCNz, LCN2 according to FIG. 5--or, respectively, three connections or three time slots are required in the case where there are two ISDN B-channel connections (voice connections).
Although it appears to be appropriate to use the C.sub.f channel from the point of view of channel capacity, the use of the C.sub.s channel is appropriate from the point of view of economy of bandwidths.
Independently of whether it is the C.sub.f channel or the C.sub.s channel which is used for setting up the connection (setting up bearers), it must be ensured (compare FIG. 5), that it is possible to change from the C.sub.f channel to the C.sub.s channel and conversely at any time (changing channels between channels of unequal channel capacity). In addition, it must be ensured that it is possible to change between a first C.sub.s channel and a second C.sub.s channel (changing channels between two channels of equal channel capacity) because of the possibility that two connections (bearers) can be set up at the same time in the ISDN system (2 B-channels).
Technical complexity
The DECT-specific RLL system must appear to be transparent to the ISDN subscriber and the ISDN network. For its internal functions such as, for example, DECT channel selection etc., it needs control criteria which must be determined by the analysis of ISDN "Layer-2/Layer-3" messages (compare printed document "Nachrichtentechnik Elektronik, Berlin 45, P2: (1991) Vol. 4, pages 138 to 143") of the network--ISDN subscriber (Terminal Endpoint TE) signalling if they are not explicitly available at the network interfaces.
To minimize the complexity, it is possible to concentrate this body of control criteria in a telecommunication interface of the telecommunication interfaces DIFS, DIPS, e.g. of the first telecommunication interface DIFS (DECT Intermediate Fixed System) and to control the other telecommunication interface in each case, in the present case the second telecommunication interface DIPS (DECT Intermediate Portable System) from there. In this constellation, the fixed system DIFS is always able to select a DECT channel structure corresponding to the ISDN service (C plane and U plane).
In the portable system DIPS, this is not possible without direct access to the ISDN layer 3. It is not able to map a TE-individual connection with C and U plane unambiguously onto a corresponding DECT channel structure from the ISDN layer 2 function alone in all situations.
Even if this were possible, there remains the problem of the difference in throughput when only the C.sub.s channel is used, which is economic with respect to bandwidths.
An approach is therefore sought which, with good economy of bandwidths and low system complexity, maps the entire D channel of an ISDN line onto a DECT channel arrangement in such a manner that the fundamental properties of the D channel are not changed and situations of congestion can be rapidly relieved.
A known design for the standardization of such a system has hitherto provided for the use of the C.sub.f channel for as long as the ISDN line is active. The central control function lies in the fixed system DIFS which controls the portable system DIPS via the C.sub.f channel. This solution is relatively simple but has the disadvantage, that the economy of bandwidths is not optimum.